Rounded Thread Chamfer

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Spindoctor
Posts: 189
Joined: Fri Sep 25, 2015 6:19 pm

Rounded Thread Chamfer

Post by Spindoctor »

I designed a non-standard thread without any pointy edges. This works fine.
rounded thread.png
rounded thread.png (5.4 KiB) Viewed 543 times
However, I also want the chamfer of the thread to be rounded. I have no idea on how to implement that, so I am left with a pointy edge at the top and the bottom
rounded thread1.png
rounded thread1.png (28.99 KiB) Viewed 543 times
What's even worse is the strange "nose" that forms at the end of the thread, where the helix leaves the body
rounded thread2.png
rounded thread2.png (58.4 KiB) Viewed 543 times
I haven't found a reliable and precise way to smooth these two things out in FreeCAD.

Can you think of a trick on how to do that?

My example file is too large to attach, so I uploaded it to my server. Please find it here:
https://nextcloud.yeara.net/s/WBXZYdnowx8EzAK

Thank you in advance!
chrisb
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Re: Rounded Thread Chamfer

Post by chrisb »

You can combine the path for the sweep from two helixes, where the end runs into the thread. To make such a path available for a sweep, use a SubShapeBinder.
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papyblaise
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Re: Rounded Thread Chamfer

Post by papyblaise »

First read yesterday's thread
include the radius in the rolling profile
https://forum.freecadweb.org/viewtopic.php?f=3&t=70986
Attachments
bolt2.FCStd
(766.75 KiB) Downloaded 9 times
Spindoctor
Posts: 189
Joined: Fri Sep 25, 2015 6:19 pm

Re: Rounded Thread Chamfer

Post by Spindoctor »

Thanks for your replies!

@chrisb
I'm sorry, but I cannot follow everything you wrote. What I get is: it would be possible to have three threads combined: one on the bottom chamfer (increasing helix), one on the straight part of the thread (constant helix) and one on the top part (decreasing helix). Is this correct so far? I'm not sure if this is exactly what I want but I'd like to give it a try.

However, I don't know which helix I could use for that (PartDesign Helix, Part Helix or Path Helix). Also I don't understand how the SubShapeBinder would help (this is probably because I never used the SubShapeBinder yet, only the ShapeBinder.

Can you help me understand that a little better?

@papyblaise
Did you refer to the other thread because of the problem of self-intersection? I ran into this problem multiple times but in the example file I added to my post I didn't have this problem.

The file that you attached still has the sharp edge at the chamfer
Screenshot 2022-08-12 132839.png
Screenshot 2022-08-12 132839.png (68.62 KiB) Viewed 376 times
It doesn't have the strange nose, but this is because your thread profile looks different than mine:

Yours
Screenshot 2022-08-12 133109.png
Screenshot 2022-08-12 133109.png (26.63 KiB) Viewed 376 times
Mine
Screenshot 2022-08-12 133212.png
Screenshot 2022-08-12 133212.png (29.26 KiB) Viewed 376 times
Or did I understand something incorrectly?
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papyblaise
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Re: Rounded Thread Chamfer

Post by papyblaise »

because of the problem of self-intersection
yes this is the problem
Now whith rounded fillet
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bolt2.FCStd
(985.67 KiB) Downloaded 6 times
chrisb
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Re: Rounded Thread Chamfer

Post by chrisb »

Spindoctor wrote: Fri Aug 12, 2022 11:34 am Can you help me understand that a little better?
I will try later to explain better with an appropriate example.
A Sketcher Lecture with in-depth information is available in English, auf Deutsch, en français, en español.
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